2.3- to 2.7-μm room-temperature cw operation of InGaAsSb/AlGaAsSb broad-contact and single-mode ridge-waveguide SCH-QW diode lasers

Abstract

In the work we continue our studies of broadened waveguide separate confinement InGaAsSb/AlGaAsSb quantum well diode lasers grown by MBE on n-GaSb substrates. To avoid the structure degradation associated with the miscibility gap in the 2.3 - 2.7 micrometer wavelength range, we used highly strained, 'quasi-ternary' InxGa1-xSb1-yAsy compounds with 0.25 < X < 0.38 and y approximately equals 0.02 as the material for QWs. From spontaneous emission measurements we have identified that the Auger process determines the rate of recombination in quantum well active region over the entire temperature range studied (15 - 110 degrees Celsius) for 2.6 micrometer lasers and at temperatures higher than 65 degrees Celsius for 2.3 micrometer lasers. Under these conditions, strong temperature dependence of Auger coefficient leads to the rapid increase of threshold current density with temperature (T0 approximately 40 degrees Celsius). In the range of 15 - 65 degrees Celsius for 2.3 micrometer devices we believe monomolecular non-radiative mechanism dominates and T0 is about 110 degrees Celsius. In addition, single-mode CW room temperature ridge-waveguide lasers with wavelength of 2.3 - 2.55 micrometer have been fabricated for the first time. The lasers display threshold currents around 50 mA with CW output powers of several milliwatts. Switching of the peak lasing position has been observed for both CW and pulsed operation and is related to second sub-band transitions. These results show that excess carrier energy distribution and their concentration are current dependent above threshold.